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Transcript
HEAT,
TEMPERATURE,
PHASE CHANGE
HEAT
A
form of energy that a substance has
because of the motion of its molecules.
- When a substance gains heat its molecules
move more vigorously.
- When a substance loses heat its molecular
action decreases.
- Absolute Zero is the point at which all
molecular motion would stop. (no heat
left!!)
TEMPERATURE
 Definition:
average kinetic energy of the
particles that make up a substance
 Temp is a measure of how hot or cold
something is.

It is measured in degrees
 The
size of degrees may vary depending on
the temperature scale (Fahrenheit, Celsius, or
Kelvin)
How is temp measured??
 Fahrenheit
 Celsius
 Kelvin
 Which
one is not metric?
Fahrenheit Scale
 Major


references points
Freezing point of water:
Boiling point of water:
 There
32ºF
212ºF
are 180ºF between freezing and boiling
points.
Celsius Scale
A
fixed point of where water freezes is the
zero point


Freezing point of water:
Boiling point of water:
 There
0ºC
100ºC
are 100ºC between freezing and boiling
points, making this scale closely linked to the
decimal system.
Kelvin
 The
temperature at which molecular
motion stops is the zero point
 Absolute Zero (no heat)
0K


Freezing point of water:
Boiling point of water:
 There
273 K
373 K
are 100 K between freezing and boiling
points making this scale closely linked to the
metric system.
Comparison of Temperature
Scales
-460º
Heat vs. Temperature

Temperature does
not always change
when heat is added
or taken away

There is no change
in temperature
during a phase
change - all heat
energy is used to
break bonds
between molecules,
not to raise the
temperature.
Are heat and temp the same?



Heat and temp are related, but they are NOT
the same!
Heat is dependent upon what kind of
material you are measuring and how much of
the material you have.
Example: Imagine that you fill a tea cup and
a bath tub with the exact same water that
has been heated to the exact same
temperature. Will they cool down at the
same rate?
What happens when heat is
applied to matter?
Particle Theory of Matter
 Everything
is made of matter which are
tiny particles that are…



in constant motion
held together by strong force
have spaces between them
States of Matter
 SOLID



Shape and volume is definite
Particle distance is packed in fixed positions
Particles vibrate in place
States of Matter
 LIQUID




Takes the shape of the container
Definite volume
Particle distance is close
Particles slide over one another freely
States of Matter
 GAS



Takes the shape and volume of the
container
Particle distance is spread out or squeezed
into a container
Particles are able to fly at high speeds in all
directions
Heat added to the states of
matter…
Changes in Matter
•
A substance changes state when its thermal
energy increases or decreases by a sufficient
amount (absorbing or releasing HEAT)
 Phase
changes are: melting/freezing,
vaporizing/condensing, and sublimation
Melting
 solid
to a liquid
*** Interesting Fact: different substances
have different melting points, it depends on
how strongly the particles of the substances
are attracted to one another
Silver melts at 962ºC
Water melts at 0ºC
Freezing
a
liquid to a solid
*** Interesting Fact: freezing is the opposite of
melting; therefore, a substances “freezing
point” is the same as its melting point
Freezing Rain
Vaporization
a


liquid to a gas
Evaporation: surface only
Boiling: throughout
Condensation
a

gas to a liquid
Interesting Fact: condensation is the
opposite of vaporization
 Examples
of condensation
are steam, clouds, and mist;
you cannot see water vapor
it is a gas
Sublimation
a
solid directly to a gas; there is not liquid
phase

Interesting Fact: an example of sublimation
is dry ice
 Dry
ice is solid carbon dioxide
that changes directly to carbon
dioxide gas when it is in room
temperature
 Label
each letter on your graph with a
phase or a phase change.
 What happens to the temperature during
a phase change?